Transfer hydrogenation applications with ruthenium nanocatalysts

In this thesis, the catalytic activity of ruthenium nanoparticles prepared by using monodentate phosphoramidite ligands containing binaphthyl skeleton with different steric properties as stabilizers in transfer hydrogenation (TH) reactions was investigated. Firstly, phosphoramidite ligands bearing binaphthyl skeleton were prepared starting from racemic 1,1'-bi-2-naphthol (BINOL) and then ruthenium nanoparticles were synthesized using these ligands as stabilizers. The ligands were characterized by nuclear magnetic resonance spectroscopy (NMR) (1H, 13C and 31P) and high-resolution mass spectroscopy (HRMS) techniques. Transmission electron spectroscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectroscopy (XRD) and thermogravimetric analysis (TGA) techniques were used for determination of ruthenium nanocatalysts. The results showed that phosphoramidite ligands are very effective stabilizers for the preparation of monodisperse ruthenium nanoparticles with very narrow and small size (1.36-1.41 nm). The catalytic activity of the synthesized ruthenium nanocatalysts was investigated in the transfer hydrogenation reaction of acetophenone to 1-phenylethanol using ammonia borane (NH3BH3) as hydrogen source. After test reactions carried out at various temperatures (25 and 60 °C) using different bases (KOH, tBuOK, tBuONa), solvents (EtOH, THF, acetonitrile) and metal loadings (3.0 and 10.0 mg), the scope of the studies was extended by substituted acetophenones. The results showed that the synthesized ruthenium nanocatalysts can effectively catalyze transfer hydrogenation reactions in only 15 minutes. Keywords: Ruthenium, transfer hydrogenation, phosphoramidite, nanoparticule. Advisor: Assoc. Prof. Mustafa Kemal YILMAZ, Department of Chemistry, Mersin University, Mersin